Field of the Invention
The present invention relates to a sheet feeding apparatus which processes sheets on which images are formed.
Description of the Related Art
As shown in Japanese Patent Laid-Open No. 2000-219399, conventionally, in an image forming apparatus, a sheet having an image formed thereon may be discharged to the stack tray after performing post-processing such as stapling.
FIG. 18 is a diagram showing a configuration of a portion for conveying a sheet during post-processing of the image forming apparatus of the prior art.
As shown in the figure, in the conventional image forming apparatus, the rear end of the sheet bundle S on the processing tray is pushed in the direction A by the sheet bundle pushing member 60a provided on the belt 60 and the sheet bundle S is discharged on the stack tray.
FIGS. 19A and 19B are diagrams showing states of pushing the rear end of the sheet bundle S by the sheet bundle pushing member 60a in the image forming apparatus of the prior art shown in FIG. 18. FIG. 19A is a diagram showing a state in which the sheet bundle pushing member 60a begins to push the sheet bundle S. FIG. 19B is a diagram showing a state immediately before the sheet bundle pushing member 60a finishes pushing the sheet bundle S.
As shown in FIG. 19A, the sheet bundle pushing member 60a provided on the belt 60 pushes the trailing end of the sheet bundle S out on to the stack tray. At this time, in the case of using a sheet with a low rigidity, the sheet is easily bent in a concave portion of the sheet bundle pushing member 60a. 
Therefore, when the sheet bundle pushing member 60a is stopped or decelerated immediately before discharging the sheet stack S on to the stacking tray, so-called spring-back is easy to occur in which the sheet bundle S bent when pushed by the sheet bundle pushing member 60a goes back to a flat state.
As shown in FIG. 19B, when spring back occurs, a problem arises wherein the sheet stack S jumps out by kicking the sheet bundle member 60a, which lowers the loading ability on the stacking tray.
It can be considered that kicking amount of the sheets is reduced by reducing the amount of deflection of the sheets by moving the sheet bundle pushing member 60a slowly. However, this causes a problem where the productivity is lowered.